Mechanisms of Autophagy Initiation Hurley, James H; Young, Lindsey N
Annual review of biochemistry,
06/2017, Letnik:
86, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Autophagy is the process of cellular self-eating by a double-membrane organelle, the autophagosome. A range of signaling processes converge on two protein complexes to initiate autophagy: the ULK1 ...(unc51-like autophagy activating kinase 1) protein kinase complex and the PI3KC3-C1 (class III phosphatidylinositol 3-kinase complex I) lipid kinase complex. Some 90% of the mass of these large protein complexes consists of noncatalytic domains and subunits, and the ULK1 complex has essential noncatalytic activities. Structural studies of these complexes have shed increasing light on the regulation of their catalytic and noncatalytic activities in autophagy initiation. The autophagosome is thought to nucleate from vesicles containing the integral membrane protein Atg9 (autophagy-related 9), COPII (coat protein complex II) vesicles, and possibly other sources. In the wake of reconstitution and super-resolution imaging studies, we are beginning to understand how the ULK1 and PI3KC3-C1 complexes might coordinate the nucleation and fusion of Atg9 and COPII vesicles at the start of autophagosome biogenesis.
Janus kinases (JAKs) are key effectors in controlling immune responses and maintaining hematopoiesis. SOCS3 (suppressor of cytokine signaling-3) is a major regulator of JAK signaling and here we ...investigate the molecular basis of its mechanism of action. We found that SOCS3 bound and directly inhibited the catalytic domains of JAK1, JAK2, and TYK2 but not JAK3 via an evolutionarily conserved motif unique to JAKs. Mutation of this motif led to the formation of an active kinase that could not be inhibited by SOCS3. Surprisingly, we found that SOCS3 simultaneously bound JAK and the cytokine receptor to which it is attached, revealing how specificity is generated in SOCS action and explaining why SOCS3 inhibits only a subset of cytokines. Importantly, SOCS3 inhibited JAKs via a noncompetitive mechanism, making it a template for the development of specific and effective inhibitors to treat JAK-based immune and proliferative diseases.
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► SOCS3 inhibits the catalytic activities of JAK1, JAK2, and TYK2 but not JAK3 ► A three-residue motif specific to JAK kinases is crucial for its interaction with SOCS3 ► SOCS3 binds JAK and cytokine receptor simultaneously ► SOCS3 is a noncompetitive JAK inhibitor
Inflammation has classically been defined histopathologically, especially by the presence of immune cell infiltrates. However, more recent studies suggest a role for "low-grade" inflammation in a ...variety of disorders ranging from metabolic syndrome to cancer, which is defined by modest elevations in pro-inflammatory gene expression. Consequently, there is a need for cost-effective, non-invasive biomarkers that, ideally, would have the sensitivity to detect low-grade inflammation and have a dynamic range broad enough to reflect classic robust intestinal inflammation. Herein, we report that, for assessment of intestinal inflammation, fecal lipocalin 2 (Lcn-2), measured by ELISA, serves this purpose. Specifically, using a well-characterized mouse model of DSS colitis, we observed that fecal Lcn-2 and intestinal expression of pro-inflammatory cytokines (IL-1β, CXCL1, TNFα) are modestly but significantly induced by very low concentrations of DSS (0.25 and 0.5%), and become markedly elevated at higher concentrations of DSS (1.0 and 4.0%). As expected, careful histopathologic analysis noted only modest immune infiltrates at low DSS concentration and robust colitis at higher DSS concentrations. In accordance, increased levels of the neutrophil product myeloperoxidase (MPO) was only detected in mice given 1.0 and 4.0% DSS. In addition, fecal Lcn-2 marks the severity of spontaneous colitis development in IL-10 deficient mice. Unlike histopathology, MPO, and q-RT-PCR, the assay of fecal Lcn-2 requires only a stool sample, permits measurement over time, and can detect inflammation as early as 1 day following DSS administration. Thus, assay of fecal Lcn-2 by ELISA can function as a non-invasive, sensitive, dynamic, stable and cost-effective means to monitor intestinal inflammation in mice.
The plant cell wall is an important factor for determining cell shape, function and response to the environment. Secondary cell walls, such as those found in xylem, are composed of cellulose, ...hemicelluloses and lignin and account for the bulk of plant biomass. The coordination between transcriptional regulation of synthesis for each polymer is complex and vital to cell function. A regulatory hierarchy of developmental switches has been proposed, although the full complement of regulators remains unknown. Here we present a protein-DNA network between Arabidopsis thaliana transcription factors and secondary cell wall metabolic genes with gene expression regulated by a series of feed-forward loops. This model allowed us to develop and validate new hypotheses about secondary wall gene regulation under abiotic stress. Distinct stresses are able to perturb targeted genes to potentially promote functional adaptation. These interactions will serve as a foundation for understanding the regulation of a complex, integral plant component.
Online citizen science projects have broadened options for accessing science and enabled different forms of participation in scientific research for adult and young volunteers. Yet, little is known ...regarding participation patterns among youth participants. Quantitative approaches were used to investigate the contribution of 183 young volunteers to citizen science on the iNaturalist platform and the participation behaviour that relates to their contribution. The participants accessed and used iNaturalist as part of one-day field-based events (bioblitzes) facilitated by museums. Compared to the observation behaviour of all iNaturalist users, as documented on the platform, the young volunteers observe fewer plants and birds, and more molluscs, arachnids and insects. The average daily contributions of young volunteers were found to be positively associated with a large proportion of active days on iNaturalist and a systematic contribution behaviour, yet negatively related to a long duration on the platform. This study enhances our understanding of young volunteers' contributions to citizen science and provides insights for research on participation in online citizen science. Our findings have implications on how museums design the field-based events to encourage follow-up systematic participation and maintain active contribution.
Mixed lineage kinase domain-like (MLKL) is a component of the “necrosome,” the multiprotein complex that triggers tumor necrosis factor (TNF)-induced cell death by necroptosis. To define the specific ...role and molecular mechanism of MLKL action, we generated MLKL-deficient mice and solved the crystal structure of MLKL. Although MLKL-deficient mice were viable and displayed no hematopoietic anomalies or other obvious pathology, cells derived from these animals were resistant to TNF-induced necroptosis unless MLKL expression was restored. Structurally, MLKL comprises a four-helical bundle tethered to the pseudokinase domain, which contains an unusual pseudoactive site. Although the pseudokinase domain binds ATP, it is catalytically inactive and its essential nonenzymatic role in necroptotic signaling is induced by receptor-interacting serine-threonine kinase 3 (RIPK3)-mediated phosphorylation. Structure-guided mutation of the MLKL pseudoactive site resulted in constitutive, RIPK3-independent necroptosis, demonstrating that modification of MLKL is essential for propagation of the necroptosis pathway downstream of RIPK3.
•The crystal structure of MLKL reveals an unusual pseudoactive site•The MLKL pseudokinase domain binds ATP but is not catalytically active•MLKL-deficient cells are resistant to TNF-induced necroptosis•MLKL pseudoactive site mutations cause caspase- and RIPK3-independent necroptosis
Flexible Laryngoscopy and COVID-19 Rameau, Anaïs; Young, VyVy N; Amin, Milan R ...
Otolaryngology and head and neck surgery/Otolaryngology--head and neck surgery,
June 2020, Letnik:
162, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Flexible laryngoscopy, the gold-standard evaluation of the larynx and the pharynx, is one of the most commonly performed procedures in otolaryngology. During the coronavirus disease 2019 (COVID-19) ...pandemic, flexible laryngoscopy represents a risk for patients and an occupational hazard for otolaryngologists and any clinic staff involved with the procedure or endoscope reprocessing. Here we present a set of recommendations on flexible laryngoscopy performance during the pandemic, including patient selection, personal protective equipment, and endoscope disinfection, based on a consensus reached during a virtual webinar on March 24, 2020, attended by approximately 300 participants from the American laryngology community.
New Findings
What is the topic of this review?
This review highlights the emerging role of disruptions in endoplasmic reticulum (ER) function, namely ER stress, as a contributor to hypertension.
What ...advances does it highlight?
This review presents an integrative view of ER stress in cardiovascular control systems, including systems within the brain, kidney and peripheral vasculature, as related to development of hypertension.
The endoplasmic reticulum (ER) is a cellular organelle specialized in the synthesis, folding, assembly and modification of proteins. In situations of increased protein demand, complex signalling pathways, termed the unfolded protein response, influence a series of cellular feedback loops to control ER function strictly. Although this is initially a compensatory attempt to maintain cellular homeostasis, chronic activation of the unfolded protein response, known as ER stress, leads to sustained changes in cellular function. A growing body of literature points to ER stress in diverse cardioregulatory systems, including the brain, kidney and vasculature, as central to the development of hypertension. Here, these recent findings from essential and obesity‐related forms of hypertension are highlighted in an integrative manner, with discussion of the potential upstream causes and downstream consequences of ER stress. Given that hypertension is a leading medical and socio‐economic global challenge, emerging findings suggest that targeting ER stress might represent a viable strategy for the treatment of hypertensive disease.
Autophagy is an important cellular degradation pathway with a central role in metabolism as well as basic quality control, two processes inextricably linked to ageing. A decrease in autophagy is ...associated with increasing age, yet it is unknown if this is causal in the ageing process, and whether autophagy restoration can counteract these ageing effects. Here we demonstrate that systemic autophagy inhibition induces the premature acquisition of age-associated phenotypes and pathologies in mammals. Remarkably, autophagy restoration provides a near complete recovery of morbidity and a significant extension of lifespan; however, at the molecular level this rescue appears incomplete. Importantly autophagy-restored mice still succumb earlier due to an increase in spontaneous tumour formation. Thus, our data suggest that chronic autophagy inhibition confers an irreversible increase in cancer risk and uncovers a biphasic role of autophagy in cancer development being both tumour suppressive and oncogenic, sequentially.
Rising temperatures are amplifying drought‐induced stress and mortality in forests globally. It remains uncertain, however, whether tree mortality across drought‐stricken landscapes will be ...concentrated in particular climatic and competitive environments. We investigated the effects of long‐term average climate i.e. 35‐year mean annual climatic water deficit (CWD) and competition (i.e. tree basal area) on tree mortality patterns, using extensive aerial mortality surveys conducted throughout the forests of California during a 4‐year statewide extreme drought lasting from 2012 to 2015. During this period, tree mortality increased by an order of magnitude, typically from tens to hundreds of dead trees per km2, rising dramatically during the fourth year of drought. Mortality rates increased independently with average CWD and with basal area, and they increased disproportionately in areas that were both dry and dense. These results can assist forest managers and policy‐makers in identifying the most drought‐vulnerable forests across broad geographic areas.
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